PTL 1 discloses “a transmission apparatus including: a signal transmission unit which transmits an image signal to a reception apparatus via a cable, by a differential signal, using multiple channels; an information transmission unit which transmits request information that requests a supply of a power source, to the reception apparatus via the cable; and a power source switching unit which supplies the power source supplied from the reception apparatus via the cable according to transmission of the request information of the information transmission unit, to an internal circuit” (see [0017] of PTL 1).
Moreover, it discloses “when the sink device 120A is connected with the source device 110A via the HDMI cable 130, (c) a +5V power source from the power source circuit 126A of the sink device 120A is supplied to the source device 110A via a reserve line of the HDMI cable 130” ([0192] of PTL 1), “the source device 110A transmits a <Request Power Supply> command that is a power source supply request to the sink device 120A via a CEC line” ([0192] of PTL 1), “when it is possible to supply a requested voltage value and current value, the sink device 120A controls the voltage value and current value of the power source from the power source circuit 126A so as to correspond to the voltage value and current value requested by the source device 110A” ([0196] of PTL 1), “afterward, when the power source via the power source line of the HDMI cable 130 is not necessary in the source device 110A, the source device 110A transmits the <Request Power Supply> command showing that the power source supply is not necessary, to the sink device 120A” ([0198] of PTL 1) and “the state of the power source supply from the sink device 120A to the source device 110A returns to the first state” ([0198] of PTL 1).
PTL 2 discloses “function information is transmitted from the source device to the sink device or from the sink device to the source device as CEC (Consumer Electronics Control) data or CDC (Capability Discovery Channel) data” via a CEC line which is a control line between the source device and the sink device connected by HDMI (HDMI and High-Definition Multimedia Interface are trademarks or registered trademarks of HDMI Licensing, LLC) (see [0160] of PTL 2).